Why is the DNA replication method called Semi-Conservative replication?
One of the strands is from the original DNA molecule and the other is formed from free-floating nucleotides in the nucleus
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This means there is g______ c_________ between generations of cells
Genetic Continuity
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What is the role of DNA Helicase in the replcation of DNA?
It catalyses the reaction to break the hydrogen bonds between organic bases holding the two polynucleotide strads together, causing the double helix to unwind into two seperate strands
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What happens to th seperate strands once they have been seperated by DNA Helicase?
Each original sugar-phosphate strand acts as a template to form a new strand by complimentary base-pairing with free-floating nucleotides in the nucleus
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Which bases match up?
Adenine and Thymine, Cytosine and Guanine
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How are the nucleotides of the new strands joined together?
By condenstaion reactions
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Which enzyme catalyses these reactions?
DNA Polymerase
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What bonds are formed between nucleotides to make up the sugar-phosphate strands?
Phosphodiester bonds
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Draw a diagram of semi conservative replication
Page 18 of Revision guide
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The DNA strands run a___________ to each other
Antiparallel
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Why does the enzyme DNA Polymerase only work in a 3' to 5' prime direction on the origanl DNA strand?
The active site of DNA Polymerase is only complementary to the 3' end of the template strand.
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True or False: The DNA pOlymerase working on one of the temlate strands moves in the opposite direction to the DNA Polymerase working on the other template strand
True
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Which two scientists provided evidence for semi-conservative replication?
Meselson and Stahl
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Which DNA replication method were they disproving?
Conservative replication
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What is the difference between conservative and semi-conservative replication?
Semi-conservative replication involves splitting the strands of the original DNA molecule and using them as templates to create two identical DNA molecules. Conservative replication just involves creating a new DNA molecule
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Wht was the first stage of Meselson's and Stahl's experiment?
Bacteria were grown in an isotope of N15 and spun in a centrifuge. All their DNA bases were made up of N15 and so due to the density of it, it settled near the bottom of the test tube
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What happened after one generation?
This N15 bateria were left to grow in an N14 medium. According to semi-conservative replication the DNA now replicated after one genertion should contain one strand of N15 and one strand of N14.
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What result would be shown after the first generation in the test tube after spinning it in a centrifuge
The DNA molecules would settle in the middle of the test tube
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Why would the DNA settle in the middle?
They contain both N15 (settles at the bottom due to higher denisty) and N14 (settles at the top due to low density), hence the densities combined leaves the replicated DNA to settle in the middle
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What would the test tube look like if conservative replication ocurred?
There would be the N15 DNA molecule settled at the bottom and the newly synthesised N14 DNA molecule at the top
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Other cards in this set
Card 2
Front
Why is the DNA replication method called Semi-Conservative replication?
Back
One of the strands is from the original DNA molecule and the other is formed from free-floating nucleotides in the nucleus
Card 3
Front
This means there is g______ c_________ between generations of cells
Back
Card 4
Front
What is the role of DNA Helicase in the replcation of DNA?
Back
Card 5
Front
What happens to th seperate strands once they have been seperated by DNA Helicase?
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